Thermochemical reactor for a cooling and/or heating apparatus

ABSTRACT

A thermochemical reactor ( 1 ) for a cooling and/or heating includes at least one reagent unit ( 2 ) which, using chemical combination, can absorb a gas stream originating from a tank and which, using the reverse chemical reaction, can desorb the gas stream due to a rise in temperature. The reagent unit ( 2 ) is disposed in a container ( 3 ) that has walls, at least some of which are equipped with diffusers ( 7 ) for distributing the gas stream. In addition, the reagent unit ( 2 ), which can be heated, is of the type that can expand during absorption of the gas stream and retract during desorption of the gas stream. Moreover, at least some of the walls are mobile walls, which can accompany the longitudinal movement of the reagent unit ( 2 ), to enable successive deformation phenomena.

BACKGROUND OF THE INVENTION

(1). Field of the Invention

The present invention relates to a thermochemical reactor for a coolingand/or heating apparatus including at least one reagent unit capable ofabsorbing, by chemical combination, a gas flow coming from a tank and ofdesorbing this gas flow by reverse chemical reaction, under the actionof a rise in temperature, so that it reintegrates into said tank, saidreagent unit being arranged in a container connected to said tankthrough a pipe, and having walls, at least some of which includediffuser means permitting to distribute the gas flow in one direction orin the other one between the reagent unit and the tank, said reagentunit being of the type capable of expanding during the absorption of thegas flow and of retracting during the desorption of the gas flow andbeing connected to heating means.

The invention also relates to a cooling and/or heating apparatusincluding such a thermochemical reactor as well as an isothermal deviceprovided, in turn, with said cooling and/or heating apparatus.

The present invention more specifically relates to the field of theproduction of cold and/or heat from thermochemical systems.

(2). Description of the Prior Art

In a known way, such systems are based on heat transfers resulting froma chemical reaction between a gas, such as ammonia, and reactive salts,such as calcium chlorides, contained respectively in two tanks separatedby a valve. When the latter opens, a chemical reaction occurs, duringwhich the gas vaporizes, in order to join the salts. This evaporation isheat-consuming and therefore generates a production of cold at the levelof the tank containing the gas. Furthermore, the chemical reactionbetween the gas and the salts is exothermic and causes heat to bereleased at the level of the salt tank.

After complete evaporation of the gas, or when the salts are saturated,the chemical reaction stops as well as the production of cold and heat.It is then possible to regenerate the system, simply by heating thereactive salts, which causes the separation of the salts and the gaswhich then returns to its original tank where it is again condensed.After regeneration of the reactive salts, a new cooling and/or heatingcycle can be performed.

The progressive implementation of these thermochemical systems in anindustrial environment has at the same time required the development ofsuitable apparatuses, having means capable of optimizing, improving andcontrolling the evolution of the thermochemical reactions, and designedby means of reliable materials capable of withstanding high stresses,namely pressure and temperature stresses.

In this context, many work related to the development of the reactor,i.e. the unit formed by the reactive salts, the envelope in which theyare contained and the various means the latter is provided with, with aview to providing a solution in which the reagent is not only capable ofabsorbing and desorbing a maximum quantity of gas without being carriedalong by this gas, but also capable of undergoing volume changes in saidenvelope, without deteriorating same or losing its reactive qualities,even bursting.

Presently, several documents are known, which are dedicated to thedescription of innovations made in this field.

Thus, FR 2 455 713 for example refers to a thermochemical reactor, whichcan be formed of several reactive bodies made self-supporting by abinder and contained in a flexible envelope having several envelopeelements. Passages provided for between adjacent envelope elementsdefine channels allowing the gas flow to circulate between the variousreactive bodies. The reactor also includes distribution structures whichcommunicate with the circulation channels and are designed so as to beadapted to the dimensional changes of an envelope element. Thesedistribution structures can include telescopic elements which can bepushed into each other in order to cause changes in length of saiddistribution structures.

Such a thermochemical reactor has the disadvantage of a complexstructure characterized by a great brittleness.

U.S. Pat. No. 2,649,700 describes a thermochemical reactor includingseveral annular-shaped elementary reagent units confined between aninner wall and a peripheral wall. Porous screens separating theelementary units from each other distribute the gas flow between thelower and higher surfaces of the latter and an inlet and outlet conduit.The elementary units are made out of sintered metal and are thusdimensionally stable, namely as regards the above-mentioned pressure andtemperature stresses.

Practice has shown that this embodiment has many disadvantages. Indeed,the metallic nature of the units highly limits the quantity of gas thatcan be absorbed and is in addition characterized by poor retention ofthe absorbing particles. This obliges to cause the gas flow to pass toofast through screens acting as filters, which complicate the structureof the unit and make it heavy.

From EP 0 206 875 is also known a reagent unit formed by a mixture ofchloride and an foamed carbon derivative, capable of absorbing highquantities of gas per volume of unit, and solving the problem of masstransfer. This solid reagent unit has however a low mechanical strengththat tends to quickly be deformed under the action of pressure gradientsand volume changes it undergoes, so that its gas retention capabilitygradually tends to decrease during the cooling-regeneration cycles.Finally, the surfaces of the reagent for the mass exchanges can bedeformed so much that they become completely ineffective.

In the solution provided by U.S. Pat. No. 2,384,460, the reactivematerial is confined between containment walls, in a limited volume, andthrough same pass perforated gas conduits filled with glass wool aimedat retaining said reactive material. Because of the close confinement,the reactive material maintains the same volume and the same shape, notonly during the saturation phase, but also during the successiveabsorption-desorption cycles.

A quite similar thermochemical reactor device is also provided in EP 0692 086, which describes namely a thermochemical reactor including asolid reagent unit confined in a container, between containment walls,some of which are pervious to mass exchanges. The characteristic of thisreactor is defined by the reagent unit used being likely to undergochanges in volume depending on the quantity of gas absorbed, while thecontainment walls are capable of ensuring the stability in shape of theunit against the tendency to said changes in volume. Thus, in thisdocument is provided to enclose a solid reagent unit in a container withstrictly adapted dimensions, so that this reagent unit maintains itsdimensions during the various absorption-desorption cycles, maintainsits initial mechanical strength, and avoids its swelling, even itsdeterioration through bursting.

It could be observed that confining the reagent inside a limited space,as described in particular in the last two documents, although madenecessary in order to avoid the deterioration of the system, inparticular in order to avoid bursting of the reagent unit, represents anobstacle to an optimal evolution of the expected thermochemicalreactions. Indeed, impeding the swelling of the reagent considerablyreduces the maximum quantity of gas which can be successively absorbedand desorbed, which has in particular a repercussion on the time ofautonomy of the system.

Another known similar device is described in the document FR 2 723 438and tries to cope with the separation of the solid reagent from thewalls of the enclosure, this separation resulting into a loss of thepower of the reaction through a drop in the thermal-transfercoefficient. To this end, a fluid is introduced between the reagent andthe walls of the enclosure, said fluid bringing about the thermalconnection between the reagent and the enclosure. In addition, afluid-confining device is added inside the enclosure in order to limitthe displacement of said fluid and to prevent it from accumulating ontop of the reagent.

This device has nevertheless the disadvantage of being of a complexembodiment, using additional means for implementing a fluid and forconfining same.

SUMMARY OF THE INVENTION

The object of this invention is thus to provide a new thermochemicalreactor, in which the swelling of reagent is not prevented, butnevertheless controlled so that its absorption-desorption capacities arefully used without fearing its deterioration through bursting.

To this end, the invention provides a thermochemical reactor for acooling and/or heating apparatus comprising at least one reagent unitcapable of absorbing, by chemical combination, a gas flow coming from atank and of desorbing this gas flow by reverse chemical reaction, underthe action of a rise in temperature, so that it reintegrates into saidtank, said reagent unit being arranged in a container connected to saidtank through a pipe, and having walls, at least some of which includediffuser means permitting to distribute the gas flow in one direction orin the other one between the reagent unit and the tank, said reagentunit being of the type capable of expanding during the absorption of thegas flow and of retracting during the desorption of the gas flow andbeing connected to heating means, wherein at least some of said wallsconsist of movable walls, capable of following the longitudinal movementperformed by the reagent unit during its expansion or its retractioninside said container, so as to enable the successive deformationphenomena by expansion and restoring to the initial shape by retractionof said reagent unit.

According to a preferred embodiment, in the invention said container isalso defined by a tube, each end of which is extended by a half-sphere,the diameter of which is such that it substantially allows insertingwithout backlash the reagent unit, which has, in turn, a cylindricalshape and is sandwiched between two discs capable of slidinglongitudinally, should the case arise, towards each half-sphere underthe action of the expansion of the reagent unit, or, should the casearise, towards the central zone of the tube under the action of theretraction of the reagent unit.

Furthermore, according to an advantageous feature, the present inventionalso provides that the diffuser means enabling the distribution of thegas flow in one direction or in the other one between the reagent unitand the tank are defined by a set of several walls imbricated into eachother, delimiting centrally a channel, each made out of materialscapable of permitting the passing through of the gas flow, said setbeing capable of being inserted through openings provided for thispurpose in said reagent unit and said movable walls, and said setcommunicating at the level of one of its ends with the pipe connectingthe container to the tank.

According to an embodiment of the invention, the thermochemical reactoris provided with heating means defined by a set of heating collars orribbons positioned outside the container in which the reagent unit isarranged.

On the other hand, this document also refers to a cooling and/or heatingapparatus including a thermochemical reactor according to the invention,connected to a gas-fluid tank by means of a pipe provided with a valve,as well as to an isothermal device provided with such a cooling and/orheating apparatus.

The present invention also relates to the features which will becomeclear during the following description, and which should be consideredseparately or according to all their possible combinations.

This description relating to exemplary embodiments, given by way of anindication and in a non-restrictive way, will permit to betterunderstand how the invention can be carried out, with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 represents a schematic perspective and exploded view of anembodiment of a thermochemical reactor according to the presentinvention,

FIG. 2 represents a schematic perspective view of a cooling and/orheating apparatus according to the invention,

FIGS. 3 and 4 represent schematic longitudinal cross-sectional views ofa thermochemical reactor according to the invention, before and afterthe absorption of gas, respectively,

FIG. 5 represents a schematic perspective view of a device provided withthe cooling and/or heating apparatus of FIG. 2,

FIG. 6 represents a schematic cross-sectional view of the thermochemicalreactor of FIGS. 3 and 4, along the line VI-VI of FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The thermochemical reactor 1 that can be seen in FIG. 1, relating to aparticular embodiment of the invention, is comprised of a solid reagentunit 2, in the form of at least four cylindrical wafers inserted into acontainer 3 defined by a tube, which is preferably made out of stainlesssteel and has a diameter adapted to guarantee a close contact betweenits inner walls 30 and the outer surface 20 of the reagent unit 2 aftertheir assembling. Furthermore, as can be seen in FIG. 3, the reagentunit 2 is slid into the tube defining the container 3 in a centered way,while providing some clearance 32 at each end 34, 35 of said tube.

Each end 34, 35 of the tube defining the container 3 is furthermoreclosed thanks to closing means 31 having the shape of a half-sphere or acap (only one of which is schematically shown in FIG. 1), which is fixedthrough welding, during the manufacture of the reactor 1.

The container 3 is connected by means of a pipe 4 provided with a valve40, and a check and/or non-return valve 41, to a tank 5, visible in FIG.2, aimed at containing a gas under pressure, for example ammonia.

Preferably, the nature of the reagent unit 2 used in a thermochemicalreactor according to the invention is based on the association of twocomponents, namely Expanded Natural Graphite (GNE), which remains inertduring the thermochemical reaction, and a reactive salt, such asalkaline, alkaline-earth, or metal salts. It could be shown that such astructure, including GNE, allowed improving the thermochemicalperformances of the method.

In the exemplary embodiment represented in FIG. 1, the reagent unit 2 isperforated with three openings, not shown, of which one central openingand two openings located on both sides of the latter, aimed at allowingthe passing through of diffuser means 7 for enabling the distribution ofthe gas flow, in one direction or the other one, between the reagentunit 2 and the tank 5, and of a sleeve 6 for accommodating heating meanssuch as a heating resistor, respectively.

One can observe, in this respect, that according to another embodiment,a thermochemical reactor according to the invention could also beprovided with heating means defined not by a heating resistor insertedinto the reagent unit 2, but by a set of heating collars or ribbonspositioned outside said container 3.

The sheath 6 of the heating resistor is conventionally in the form of astainless steel tube, which passes through the container 3, and is fixedat the level of its two ends to the bottoms of the closing means 31 inthe form of half-spheres, while the diffuser means 7, the structure ofwhich, which represents another specificity of this invention, is in theform of an assembly of several pervious walls.

Thus, these diffuser means 7 are more specifically defined by a set ofseveral walls imbricated into each other, delimiting a channelcentrally, each made out of materials capable of allowing the passingthrough of the gas flow, said unit being capable of being insertedthrough openings as mentioned above, provided for this purpose in saidreagent unit 2. Said set of walls communicates at the level of one ofits ends with the pipe 4 connecting the container 3 to the tank 5 andconveying the gas flow between these two elements.

In fact, the unit forming the diffuser means 7 includes namely an innerwall defined by a profile bar with a triangular cross-sectionmanufactured after folding a perforated sheet at two points, for exampleof the R2T4 type, as well as a median wall formed by a stainless steelfabric, the size the meshes of which is preferably between 10 micronsand 100 microns, wound around the perforated sheet. Finally, the unitalso includes an outer wall, defined by a porous tube of stretchedmetal, the pore size of which is preferably between 100 microns and 800microns.

On the other hand, according to the invention, this set of several wallsincluding diffuser means 7 has a length substantially identical to thatof the tube forming the container 3, so that each of its ends entersinto contact with the bottom of each half-sphere of the closing means31.

In a known way, the diffuser means 7 play an essential role for theevolution and reproducibility over time of the thermochemical reaction.The structure given to the diffuser means 7 within the framework of thisinvention has, for this purpose, multiple advantages. Indeed, theperforated sheet prevents the diffusion openings provided for in thereagent unit 2 from clogging, while the stainless-steel fabric is usedas a filter capable of retaining in the reagent unit 2 possible grainsof salts sucked into the circuit at the opening of the valve 40. Inaddition, the stretched metal tube prevents the tensions due to theexpansion of the reagent unit 2 from passing through the stainless-steelfabric, through the holes in the perforated sheet.

Because of such a structure of the thermochemical reactor 1, thematerial forming the reagent unit 2 is thus radially confined betweenthe inner wall 30 of the container 3, the wall of sheath 6 and the outerwall of the set of walls including the diffuser means 7.

Advantageously, according to the invention, the reagent unit 2 isfurthermore sandwiched between two discs 8 provided with openings 80,81, 82 for the passing through of the sheath 6 and the diffuser means 7,respectively, these openings 80, 81, 82 being located in front of theopenings provided for the same reasons in the reagent unit 2.

According to the invention, these discs 8 advantageously define movablewalls capable of sliding longitudinally and following the movement ofthe reagent unit 2, should the case arise, towards the closing means 31,along the clearance 32, under the action of an expansion of the reagentunit 2 during the production of cold, or towards the central zone 33 ofthe container 3 under the action of a retraction of the reagent unit 2during its regeneration.

According to a preferred embodiment, the discs 8 are applied against oneof the lower 21 or upper 22 faces, respectively, of the reagent unit,which they are made integral with through adequate means for makingintegral.

Conventionally, at the opening of the valve 40, the gas maintained underpressure in liquid state within the tank 5 evaporates and is diffusedthrough the diffuser means 7 towards the salts of the reagent unit 2,which fix same, while being capable, according to the invention, ofexpanding longitudinally, as can be seen when referring to FIGS. 3 and4. The evaporation of the gas causes the production of cold at the levelof the tank 5, whereas the exothermic reaction between the gas and thesalts simultaneously leads to a release of heat at the level of thecontainer 3. When the salts of the reagent unit 2 are fully saturated,the heating resistor is connected to the mains, in order to cause asupply of heat and the desorption of the gas, which flows back, throughthe check valve 41, to the tank 5, where it re-condenses, while thereagent unit 2 retracts to adopt its initial volume.

Permitting the reagent unit 2 to breathe and expand longitudinally alongthe clearances 32 advantageously allows avoiding the problems ofdeterioration of the reactor feared with the traditional devices, inparticular because this allows avoiding the high pressure stresses thediffuser means 7, which traditionally also act as containment walls, aresubjected to.

On the other hand, according to another feature of the invention, thediscs 8 have a diameter substantially identical to the inner diameter ofthe tube defining the container 3, and are thus capable, each, ofabutting against the inner wall of said tube at the level of eachclosing means 31, because of the narrowing of the diameter of the tubeat this location, in order to stop the movement performed by the reagentunit 2 during its expansion and to prevent it from entering into contactwith the bottom of each closing means 31.

Thus, the presence of the discs 8 advantageously prevents the ends ofthe diffuser means 7 from being clogged during the expansion of thereagent unit 2.

The invention also relates to a cooling and/or heating apparatus 10,such as for example the one schematically shown in FIG. 2, whichincludes two thermochemical reactors 1 having the features previouslydescribed, each of them being connected to a gas-fluid tank 5 by meansof a pipe 4 provided, in turn, with a valve 40 and a check valve 41.

When referring to FIG. 5, such a cooling and/or heating apparatus 10 canbe adapted onto an isothermal device 100 having a box 101 aimed atreceiving the products to be maintained at temperature and towards theinside of which said tank 5 producing the cold is oriented.

What is claimed:
 1. Thermochemical reactor for a cooling and/or heatingapparatus comprising: a tank for containing a gas, at least one reagentunit capable of absorbing, by chemical combination, a gas flow comingfrom the tank and of desorbing the gas flow by reverse chemicalreaction, under the action of a rise in temperature, so that the gasflow reintegrates into said tank, a container connected to said tankthrough a pipe, said reagent unit being arranged in said container, saidcontainer having walls, at least some of which include diffuser meanspermitting to distribute the gas flow in one direction or in the otherone between the reagent unit and the tank, heating means to which saidreagent unit is connected, wherein said reagent unit is formed of amaterial that expands during the absorption of the gas flow and retractsduring the desorption of the gas flow, wherein the walls of thecontainer include (i) a tube within which the reagent unit is introducedwithout radial play in a radial direction of the tube, an outer radialsurface of the reagent unit being in close contact with an inner radialsurface of the tube in a radial direction of the tube, so that thereagent unit performs movements in a longitudinal direction of the tubeduring its expansion and its retraction inside said container, and (ii)movable walls between which the reagent unit is sandwiched, wherein eachof the movable walls has an internal face oriented transversally withrespect to the longitudinal direction of the tube and is movable withinthe tube along a longitudinal direction of the tube, the respectiveinternal faces of the movable walls being applied against and integralwith respective opposite end faces of the reagent unit in a longitudinaldirection of the tube, so that the movable walls move in thelongitudinal direction of the tube following the movements performed bythe reagent unit in the longitudinal direction of the tube during itsexpansion and its retraction inside said container, so as to enable thesuccessive deformation phenomena by expansion and restoring to theinitial shape by retraction of said reagent unit.
 2. Reactor accordingto claim 1, wherein the container is defined by the tube, each end ofwhich is extended by closing means in the form of at least onehalf-sphere and the diameter of which is such that the tube allowsinserting substantially without backlash the reagent unit, which has, inturn, a cylindrical shape and is sandwiched between the movable wallsdefined by two discs capable of sliding longitudinally, should the casearise, towards each closing means under the action of the expansion ofthe reagent unit, or, should the case arise, towards the central zone ofthe tube under the action of the retraction of the reagent unit. 3.Reactor according to claim 2, wherein the discs have a diameteridentical to the inner diameter of the tube defining the container, andare thus capable, each, of abutting against the inner wall of one of theclosing means, in order to stop the movement performed by the reagentunit during expansion of the reagent unit and to prevent the reagentunit from entering into contact with the bottom of each closing means.4. Reactor according to claim 2, wherein the discs are applied againstone of lower or upper faces, respectively, of the reagent unit. 5.Reactor according to claim 1, wherein the diffuser means enabling thedistribution of the gas flow in one direction or in the other onebetween the reagent unit and the tank are defined by a set of severalwalls imbricated into each other, delimiting centrally a channel, eachmade out of materials capable of permitting the passing through of thegas flow, said set being capable of being inserted through openingsprovided for this purpose in said reagent unit and said movable walls,and said set communicating at the level of one of its ends with the pipeconnecting the container to the tank.
 6. Reactor according to claim 5,wherein a set of several walls has a length identical to that of thetube defining the container, so that each of ends of said set entersinto contact with the bottom of each of the closing means.
 7. Reactoraccording to claim 1, wherein the heating means are defined by a set ofheating collars or ribbons positioned outside the container.
 8. Coolingand/or heating apparatus comprising a thermochemical reactor accordingto claim 1 connected to a gas-fluid tank by means of a pipe providedwith a valve.
 9. Isothermal device equipped with a cooling and/orheating apparatus according to claim
 8. 10. Reactor according to claim1, wherein the mobile walls are entirely within the tube.